Add some support for promptly purging pages.

third_party/WebKit/Source/platform/heap/PagePool.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "platform/heap/PagePool.h"
 
 #include "platform/heap/Heap.h"
 #include "platform/heap/PageMemory.h"
 #include "platform/wtf/Assertions.h"
 
@@ skipping 10 matching lines @@
     while (PoolEntry* entry = pool_[index]) {
       pool_[index] = entry->next;
       PageMemory* memory = entry->data;
       DCHECK(memory);
       delete memory;
       delete entry;
     }
   }
 }
 
-void PagePool::Add(int index, PageMemory* memory) {
+void PagePool::Add(int index,
+                   PageMemory* memory,
+                   DecommitMemoryTiming decommit_hint) {
   // When adding a page to the pool we decommit it to ensure it is unused
   // while in the pool.  This also allows the physical memory, backing the
   // page, to be given back to the OS.
-  memory->Decommit();
+  memory->Decommit(decommit_hint);
   PoolEntry* entry = new PoolEntry(memory, pool_[index]);
   pool_[index] = entry;
 }
 
 PageMemory* PagePool::Take(int index) {
   while (PoolEntry* entry = pool_[index]) {
     pool_[index] = entry->next;
     PageMemory* memory = entry->data;
     DCHECK(memory);
     delete entry;
     if (memory->Commit())
       return memory;
 
     // We got some memory, but failed to commit it, try again.
     delete memory;
   }
   return nullptr;
 }
 
 }  // namespace blink